The brown marmorated stink bug, Halyomorpha halys, is a pest that was accidentally introduced into the United States from its native range in Japan, Korea, and China. The word ‘marmorated’ refers to its marble-like coloration (Figure 1). The brown marmorated stink bug feeds on fruits, seeds, stems, and leaves of a wide range of plants. It is also a nuisance pest that invades buildings in the autumn.
History and Geographic Range
The brown marmorated stink bug was first identified in the United States in 2001 from a specimen collected in 1998 in Allentown, Pennsylvania. By 2020, it had spread to 46 states as well as four Canadian provinces. It was first documented in Ohio in December 2007, in Franklin County. Since then, it has been documented in 62 of Ohio’s 88 counties, and likely can be found in all Ohio counties. It is a well-known hitchhiker in cargo in cars, trucks, planes, and railcars, traveling from city to city where it quickly can establish new populations. As of 2020 in Ohio, the brown marmorated stink bug can be found at high density in crops and buildings in some areas, but is often found at low density in crops and buildings in many other areas.
The first reports of damage by the brown marmorated stink bug in Pennsylvania were on ornamental plants such as butterfly-bush and paulownia (empress tree), and on backyard peach and pear trees. Beginning in 2006, commercial fruit growers reported damage in apple and pear orchards in Pennsylvania and New Jersey, and this pest soon was found in high populations in soybeans. Unusually large populations caused devastating damage to apple and peach orchards across the mid-Atlantic region in 2010. Based upon its known habits, this pest is likely to continue invading agricultural land, and will pose a risk to crops as it continues to expand its geographic range and increase its population density.
The brown marmorated stink bug is highly mobile and can switch hosts through the season, moving from plants with early-ripening fruits to those with late-ripening fruits. Because it has a broad host range, almost any crop that has fruit or immature seeds is at risk of attack.
There are 175 reported host plants of the brown marmorated stink bug in the United States, including many that are economically important crops. Below are some of those on which the bugs are most commonly found:
- Fruit crops: peach, apple, pear, Asian pear, cherry, grape, raspberry, blackberry, blueberry.
- Vegetable crops: sweet corn, peppers, tomatoes, eggplant, okra, green beans, peas, swiss chard.
- Agronomic crops: soybean, field corn, sorghum, sunflower.
- Ornamental trees: catalpa, redbud, Japanese tree lilac, crabapple, mulberry, black cherry, tree of heaven, maples.
- Ornamental shrubs: serviceberry (juneberry, shadbush), rose of Sharon.
Damage to Crops
Stink bugs are members of a large group of insects called the true bugs, which are characterized by piercing-sucking mouthparts. Like other true bugs, the brown marmorated stink bug feeds by sucking on plant juices with its beak—also called a proboscis—which is made of straw-like mouthparts. Its beak is longer than those found on most stink bug species and is strong enough to penetrate the bark of trees. Its damage to plants can range from mild to severe, depending on how long it stays at one feeding site.
Damage to Fruit Crops
In apples, stink bug damage appears as a series of discolored irregular depressions in the fruit surface, either black or dark green over the whole spot, or dark only along the edges of the spot (Figure 2). When the fruit skin is cut, the area beneath the skin is light brown and has a pithy texture (Figure 3). This is commonly confused with the physiological disorder cork spot. The edges of the affected area are typically more irregularly shaped in stink bug damage than in cork spot.
When peach fruit is damaged early in the season, the result is dark blotches on the fruit surface, sometimes with gummosis (a gummy oozing of sap) and sometimes with cat-facing, which is grooves or distorted brown lines on the fruit surface. It can be difficult to distinguish this from injury caused by other pests, such as tarnished plant bug, plum curculio, and Oriental fruit moth. In the case of stink bug injury, there will be no resulting larvae inside the fruit as there are with plum curculio and Oriental fruit moth. Peach fruit damaged by stink bugs in late summer can have lesions that look like water-soaked spots on the surface, and the fruit flesh is corky and white underneath the spots. Damage on fruit can be compounded by secondary infections and scarring as the fruit matures.
Damage to Vegetable Crops
In sweet corn, the developing immature kernels are sucked dry by stink bugs feeding through the husk (Figure 4), leaving a condition similar to dented corn but with irregular shrinking of kernels (Figure 5). In both red and green tomato fruit, stink bug feeding produces a cloudy spot blemish on the fruit surface, with thick, white, corky tissue beneath the skin. This makes the fruit unacceptable for processing. In bell pepper, the feeding also produces a cloudy spot blemish. On green beans, feeding injury to the bean pod results in light green splotches, necrotic spots, and secondary infections.
Crops that are at low risk for damage by this pest are cucurbits (cucumbers, squash, pumpkin), cole crops (broccoli, cauliflower, cabbage), onions, and potatoes.
Damage to Agronomic Crops
On soybeans, damage is found on seeds within the pods during pod fill (Figure 6). Early injury results in seeds failing to develop, while later feeding causes seed to shrivel. Injury is most common at field edges—resulting in “stay green” syndrome around the edges of damaged fields—because the feeding delays crop maturity and leaf drop. Other Ohio stink bug species, such as the green stink bug, red-shouldered stink bug, and brown stink bug, may also cause this effect.
On field corn, stink bugs feed predominantly on the developing kernels within the ear by inserting their piercing mouthparts through the husk. This leaves the kernels with a shrunken appearance.
Its additional status as a nuisance pest makes the brown marmorated stink bug different than other plant-feeding stink bug species. Adult stink bugs enter homes and other buildings in the autumn when seeking sheltered sites to spend the winter. These stink bugs do not bite people or pets, but when disturbed, can produce a characteristic pungent acrid odor that many people find offensive. The bugs can become a nuisance when they congregate in large numbers inside and outside of buildings, where they can startle people by flying around, bumping into walls, and landing on lamps, TVs, and computer screens. In extreme cases, hundreds can invade a home. They enter buildings through any small opening, mostly around windows, chimneys, and air conditioner units. They are more likely to be in attics and upper stories than in basements or lower stories of buildings.
Adults of the brown marmorated stink bug have the typical shield shape of stink bugs. They are approximately 15 mm (5/8 inch) long and 8 mm (3/8 inch) wide, about the size of a human thumb nail. The upper side of the body has mottled shades of brown and gray and is covered with dense puncture marks (Figure 7A). The underside of the body is white, sometimes with grey or black markings (Figure 7B). They have dark, reddish-brown eyes. The legs are brown with faint white banding.
The adults of the brown marmorated stink bug can be distinguished from most other species of stink bugs by the alternating dark and light bands on the last two segments of the antennae. The exposed side edges of the abdomen have alternating light and dark banding that is more prominent than in other stink bug species.
Eggs are pale green, barrel-shaped, and found in clusters of about 28 eggs (Figure 8). The immature stages, called nymphs, are oval-shaped and somewhat tick-like in appearance. Young nymphs are usually half black and half orangish-red when they emerge from eggs (Figure 9). After they molt, they are brown to black, mottled with dull red bands and yellow spots (Figure 10). Older nymphs are similarly colored, but larger in size (Figure 11). Nymphs have light bands on dark legs and antennae. The legs are more noticeably banded on nymphs than on adults.
The brown marmorated stink bug overwinters in the adult stage in houses, barns, woodpiles, and other protected places. The adults begin to fly to these overwintering sites in early September, with peak flight activity in late September or early October.
Adults emerge from their overwintering sites in the spring, usually early May. After they feed for about two weeks, they mate, and the females begin to lay eggs. Eggs are laid in clusters on the underside of leaves from June to August. A single female can lay up to 400 eggs. Eggs hatch in four to seven days.
The nymphs pass through five instars (sub-stages), with a molt between each instar. Each instar lasts about one week, before the final molt into the adult stage. New adults start to appear in late July or August. There is usually one generation per year in Ohio, with the possibility of a second generation in a warmer than average year.
Monitoring and Action Threshold
Stink bug populations can be monitored with a clear sticky panel on a wooden stake (Figure 12), baited with a standardized dual (two-part) pheromone lure that is specific to the brown marmorated stink bug (Figure 13). The lure attracts adult males, adult females, and nymphs. Instead of placing the traps directly in the crop field, the current recommendation is to place them at the edge of a woods or treeline that borders the susceptible crop. Active monitoring for this pest in Ohio has been done since 2011—with the help of Extension Educators and growers across the state—primarily in fruit and vegetable crops, but in soybean and field corn as well. Traps usually detect peak numbers in August and September.
An action threshold has been established for apples using two clear, sticky traps per orchard. One trap is placed at the orchard edge and one in the interior of the orchard block. When the cumulative catch in either trap reaches four stink bugs, it is time to spray that block with insecticide and reset the trap counts to zero.
Management in Crops
Studies have shown that native, natural enemies are unable to exert much control of the brown marmorated stink bug in the United States. In its native land in Asia, populations of the pest are suppressed by a common egg parasitoid, the samurai wasp (Trissolcus japonicus). This species of tiny wasp has found its way to the United States; it was first detected in Maryland in 2014 and Ohio in 2017. As of 2020, the samurai wasp has been detected in 12 states. It lays its eggs in the eggs of the stink bug (Figure 14), and as the wasp larvae develop, the stink bug eggs turn black and die (Figure 15). Biological control by the samurai wasp is starting to occur in areas where this exotic parasitoid has spread on its own. There is hope that as the samurai wasp spreads across the United States, it will help suppress populations of the brown marmorated stink bug.
Researchers across the country are studying the biology of this new pest and testing insecticides and other tactics for its control. In general, pyrethroid and neonicotinoid insecticides are effective; but, many of these are harmful to non-target organisms and are thus not compatible with modern integrated pest management (IPM) practices in most crops. Other management tactics—such as trap-and-kill along orchard perimeters, trap cropping with a perimeter of sunflower or sorghum in vegetables, and row covers on vegetables—show promise for effective non-chemical control. More research is needed to develop and refine tactics that can effectively manage this new pest species.
The brown marmorated stink bug can be mechanically excluded from homes and buildings by sealing cracks and other openings in buildings. If bugs are entering the living areas of the home, the openings where the insects gain access first should be located and sealed. Typical entry points include cracks and crevices around window and door trim, window-mounted air conditioners, exhaust fans, ceiling fixtures, baseboards, and chimneys. Cracks or openings should be sealed with caulk to prevent entry by stink bugs. Torn window screens should be repaired, and window-mounted air conditioners should be removed for the winter.
Live and dead stink bugs can be removed from buildings with a vacuum cleaner or shop vac, and the vacuum bag should be promptly removed and discarded. Because these bugs are attracted to light, turning on a single light in a room can allow them to be captured as they approach the light, using a jar or bottle. Trapped bugs can be disposed of by throwing them outside or by placing them in a sealed container in a trash can.
Insecticides should not be used inside houses after the insects have gained access. Using an insecticide indoors is not recommended because this will not stop additional invasions, and exposure of humans and pets to pesticides should be avoided.
Resource for More Information
Stop BMSB, Specialty Crop Research Initiative, National institute of Food and Agriculture, United States Department of Agriculture, stopbmsb.org
The original version of Brown Marmorated Stink Bug fact sheet FS-3824-08 was published in 2008 and written by Celeste Welty, David Shetlar, Ron Hammond, Susan Jones, and Barbara Bloetscher (all of The Ohio State University Dept. of Entomology), and Anne Nielsen (Rutgers University Dept. of Entomology).